Masonry saw



June 19, 1951 M, E, MOGRATH 2,557,672

MASONRY SAW Filed Feb. 18, 1949 FIG. 2. 32

I NVENTOR MARTIN E. M0 GRATH,

A TTORNE Y.

Patented June 19, 1951 UNITED STATES PATENT OFFICE MASONRY SAW Martin E. McGrath, Webster Groves, Mo.

Application February 18, 1949, Serial No. 77,107

1 Claim. 1

My invention relates to machines for cuttin masonry objects, such as bricks and tiles, and has special reference to improvements in the operating and control mechanisms of such machines.

The present invention pertains to masonry saws of the kind having rotary cutting blades or discs of abrasive material. The blade is driven at high velocity and is mounted on a rocker arm or beam so that it can be moved vertically toward and from the object to be out, which object is disposed on a carriage for horizontal movement toward and from the blade. The raising and lowering of the blade is usually accomplished by means of a pedal so that both hands may be used for controlling horizontal movement of the work. In machines as now constructed the pedal is also used for applying a force to the blade and the contact pressures between the blade and the work is determined by the degree of force applied by the operator to the pedal. One disadvantage is that some operators, in order to increase the cutting rate, apply excessive force to the blade, resulting in frequent breakage.

The object of my invention is to provide an improved mechanism for controlling movement of the cutting blade toward and from the work, and for regulating the pressure of the blade on the work, all to the end of improving the operating elficiency of the machine and for prolonging the life of the blade.

In the drawing illustrating a practical, working embodiment of the invention,

Fig. l is a side elevational view;

Fig. 2 is a front elevational view;

Fig. 3 is a fragmentary sectional view as taken at line 3-3 of Fig. 1, and

Fig. 4 is a fragmentary sectional view as taken at line l4 of Fig. 3.

Referring now by characters of reference to the drawings, the frame structure of the machine includes a rectangular pan-like table top 9 having upstanding side flanges l 0, a front end flange I l and a splash guard or plate [2 at the rear end. The table top is supported at the corners by front legs l3 and rear legs l4. The rear legs extend upwardly beyond the level of the table to provide standards [5 and I6 that support a rocker arm or beam 11. The side flanges ll] of the table top constitute guide rails on which travel the four wheels 18 of a work carriage I9. Thiscarriage has a transverse work positioning bar 20 thereon and is adapted to receive a tile or other article to be cut by the saw, and to move the article in a fore-and-aft direction below and into cutting relation with the cutting blade 21 which is rotatably 2 mounted on the forward end portion of the rocker arm. The table legs [3 and I4 are connected together by an X-shaped brace 22.

The rocker arm or beam I! is an elongated steel plate having downturned side flanges and is. pivotally mounted on the upper ends of the standards 15 and I6 by a transverse shaft 23. This shaft is preferably fixedly secured to the beam II as by welding. One end of the shaft is journalled in a circular opening formed in the standard 16 and the other end is seated in a bearing recess 24 formed in the upper end of standard l5. By lifting the shaft end out of the bearing recess 24 and shifting the rocker arm assembly laterally to withdraw the shaft from the bearing opening in standard 16 the rocker arm assembly may be readily removed from the frame structure, as for purposes of shipment.

When certain types of cutting discs are used, for example, diamond edge blades, it is desirable to immobilize the beam I! to hold the blade in fixed position. Such is accomplished in the presently described machine by the provision of a sector plate 25 secured as by welding to the end of shaft 23. Plate 25 has an arcuate slot 26 and is adapted to be clamped to the sandard l5 by a handled nut 2'! on a bolt that extends through the standard and through the arcuate plate slot 26.

With certain other types of blade, as for example, corborundum disc cutters, it is desirable to permit of blade displacement during the cutting operation. With such blades it is customary to lower the cutting disc to a position of contact with the upper surface of the work and thereafter to move the work back and forth while maintaining a constant uniform downward pressure of the blade thereon, to produce successive relatively shallow cuts in the work. In this methe 0d of operation the clamping nut 21 is released from the sector plate so that the beam is free to rock under the action of the springs and pedal control mechanism to be subsequently described.

The cutting blade 2| is mounted on a transverse shaft 28 journalled in suitable bearings at the forward extremity of the beam. A sheave 29 fixed to shaft 28 is connected by a belt 30 to a drive sheave 3| on the shaft of an electric motor 32 mounted on an end portion of the beam which extends rearwardly beyond the pivotal axis. The motor is preferably positioned so that the weight loading of the beam effects an approximate balancing thereof. A safety guard or shield member 33 extends about the upper portion of the blade.

The beam I7 is adapted to be moved to raise and lower the blade with the aid of springs hereafter designated, under the control of a pedal lever 34 pivoted by a pin 35 to a vertical frame member 36 at the rear of the machine. The lever 34 extends between the legs to the front of the machine for convenient access by the operators foot and is connected by a pin 31 and vertical link 33 to an intermediate lever 39, also fulcrumed to the frame member 36. The intermediate lever is connected by a vertical link 49 to the rear end of the beam ll. Link 40 is provided at its lower end with a series of holes 4! to receive the pivot pin 42 that connects such link to the rear end of the intermediate lever, and the effective length of link All may be varied by re-locating the pin 42 in any one of these holes. By changing the effective length of link 40 as aforesaid the operating range of the blade may be shifted vertically, as for purposes of adapting the blade to objects that vary greatly in thickness or depth, and also to compensate for reduction in blade diameter as the same is worn away by use. Under normal conditions of operation, vertical adjustment and displacement of the blade is accomplished by operation of the control pedal 34.

The link 40 is provided at its upper end with a vertical slot 41 through which extends a pin 48 secured to the rear end of the beam IT. This pin is normally in contact with the link 40 at the upper end of the slot 41, but is capable of movement along the slot. Accordingly, the pin and slot afford a lost-"notion connection such that the beam, under certain conditions, is permitted to move independently of the foot lever.

Relative movement of the beam IT with re spect to the foot lever 34 is normally restrained by the provision of two springs which tend to maintain the pin 48 at the upper extremity of the slot. One of these is a tension spring 49 connected at its lower end to an eye-bolt 50 to a center portion of the foot lever, and at its upper end to the X-shaped frame brace 22 by means of a tension-adjustment screw and nut assembly 5|. The spring 49 normally holds the foot lever in a raised or retracted position against an adjustable stop member 58 attached to and de pending from the frame brace 22. The second spring, designated 52, is of torsional variety and disposed on the shaft 23 at one side of the beam [1. One end of spring 52 is attached to the beam I! at 53 and the opposite end is secured to an adjusting collar 54, rotatably mounted on shaft 23 and disposed adjacent the standard IS. The collar 54 has a series of radial bores 55 in its cylindrical surface and is adapted to be locked against turning relative to the shaft by a removable pin 55 that extends through a hole in the standard l5 and into one of the bores 55. Adjustment of spring 52 to increase or decrease the degree of force thereof applied to the beam is accomplished by removing the looking pin 56, turning the collar 54 by means of a suitable tool to obtain the desired pre-stressing of the spring, and re-installing the locking pin 56 as aforesaid to hold the collar in the position of its angular adjustment.

Spring 52 acts on the beam in a direction tending to move the cutting disc downwardly or toward the table top, and normally supplies the force and determines the degree thereof with which the cutting disc is applied to the workpiece. The magnitude of such force can be varied by an adjustment of the collar 54 as has been explained. The spring 49, acts through the foot lever and subsequently through link 40 to elevate the cutting disc, or to move the same in a direction away from the work-piece. It will thus be observed that the springs 49 and. 52 act on the beam in directions to move the same in relatively opposite directions, and normally cause the pin 48 to engage the upper extremity of slot 41 in link 49. The springs are adjusted so that in the absence of foot pressure applied to control lever 34 spring 49 will exert a dominating influence on the beam and cause the cutting disc 2| to be held in an elevated position.

In order to lower the cutting disc to bring it into engagement with a work-piece on the carriage the pedal is depressed to move the same against the action of spring 49. This effects a lifting of the upper end of slot 41 which permits the rear end of the beam to be raised, with attendant lowering of the cutting disc, under the influence of spring 52. When the pin 48 is freed of the restraining influence of link 40, as aforesaid, the force exerted on the beam and hence the cutting pressure of the blade on the workpiece is determined by spring 52. By appropriate adjustment of the spring 52 by collar 54 the cutting pressure can be regulated so that the cutter will operate with optimum efiiciency and with regard to preventing damage to the blade. Moreover, the slot and pin connection permits the blade to yield upwardly in the event that it engages an exceptionally hard spot in the workpiece.

When foot pressure is removed from the pedal spring 49 assumes control of the beam movement. The force on the beam applied by this spring overcomes the oppositely directed force applied to the beam by spring 52, causing the forward end of the beam to raise so that blade will be clear of work-piece.

Having described my invention, what I claim and desire to secure by Letters Patent is:

In a masonry saw of the character described including a frame, a work supporting platform thereon, a beam pivoted to the frame above the platform, a rotary blade and means for driving the same, mounted on'said beam, a foot lever pivoted to the frame, means operatively connecting said foot lever to the beam, said means including a link having a slot therein and a member fixed to the beam and slidable in said slot, a spring connected to said beam and acting thereon to move the blade toward the platform, and a second spring associated with said foot lever, said second spring acting on the beam in opposition to the first said spring.

MARTIN E. MCGRATH.

REFERENCES CITED UNITED STATES PATENTS Name Date Martin Nov. 21, 1939 Number 

